In process automation technology, field devices are often applied, which serve for registering and/or influencing process variables. Examples of such field devices are fill level measuring devices, mass flow measuring devices, pressure- and temperature measuring devices, etc., which as sensors register the corresponding process variables, fill level, flow, pressure, and temperature, respectively.
Referred to as field devices are, in principle, all devices, which are applied near to the process and deliver, or process, process relevant information.
A large number of such field devices are produced and sold by the firm, Endress+Hauser.
The fill level in a container or tank can be exactly measured with the help of radar measurement apparatuses based on FMCW radar. In the case of radar measurement in a pipe or tube, however, special effects occur, because the pipe or tube acts as a hollow conductor for the radar waves. Propagation of radar waves is different in hollow conductors.